Tape cassettes having overlapping reels are known in the industry as "U-matic" tape cassettes. U-matic tape cassettes are described in U.S. Pat. Nos. 4,163,533 (the '533 patent) and 4,022,401 (the '401 patent). Such cassettes generally comprise a cassette box for housing a length of magnetic recording tape helically wound on a supply reel and a take-up reel. The reels are rotatably mounted in the cassette box for transferring the tape between the reels. The take-up reel comprises a hub which is formed with an upper flange extending radially outward from the top end of the hub. The supply reel comprises a hub which is formed with a lower flange extending radially outward from the bottom end of the hub. The reels are disposed in a side by side relationship such that a portion of the upper flange overlaps a portion of the lower flange.
Because the take-up reel has only one flange effective for guiding the magnetic tape wound on the take-up reel, the bottom wall of the cassette box has a raised portion for guarding the tape wound on the take-up reel. Similarly, because the supply reel has only a single flange effective for guiding the tape wound on the supply reel, the top wall has a depending portion for guiding the tape wound on the supply reel.
As the tape is guided by the raised portion or the depending portion, the edge of the magnetic tape may skive off shavings from the surface of the cassette box. This debris can collect on the tape and cause dropouts during recording or playback. Additionally, the edge of the magnetic recording tape may become frayed as the tape is guided by the raised portion or the depending portion. This, too, can impair magnetic performance during recording or playback.
To prevent such skiving of the cassette box and such fraying of the magnetic tape, both the raised portion and the depending portion are each covered with a low-friction, wear-resistant wear pad. The '533 and '401 patents disclose -wear pads having a low-friction, wear-resistant layer comprising polytetrafluoroethylene (sold commercially under the trade name Teflon). There continues to be a need for improved wear pads which show low-friction and wear-resistant characteristics comparable to or better than polytetrafluoroethylene, but which are more economical to produce.